Field of the Invention
This invention relates to multilayer detergents in lock form, more especially for dishwashing machines; to a process for producing the detergents; and to the use of the detergents in the automatic prerinse and main wash cycle of domestic dishwashing machines (DDWM).
Heretofore, it has been standard practice to introduce the detergents used for dishwashing in DDWM, irrespective of their aggregate state and/or their form, through a dispenser generally accommodated in the door of the machine which automatically opens when the main wash cycle is reached after the prerinse cycle, so that the automatically heated tapwater flowing in is able to take up and dissolve the detergent. The detergent is required to dissolve as quickly as possible so that it is available throughout the wash cycle. The prerinse cycle is only used for cleaning to the extent that soil loosely adhering to dishes is removed by the water circulation mechanics. No detergent is used in the prerinse cycle.
It is known from institutional dishwashing, for example in large kitchens, that the main-wash detergent, which is carried over into the so-called preliminary clearing zone which corresponds to a prerinse cycle by the continuous operation of the machine on the counter-current principle, is used in that zone for the supportive removal of adhering food remains. A detergent-containing preliminary clearing zone is more effective than a preliminary clearing zone merely supplied with fresh water. However, the detergents used in this field are very strongly alkaline, containing above all alkali metal hydroxides. The pH value at normal in-use concentrations is above about 12.
Although it would be possible to introduce a known dishwashing detergent into the dispenser of the machine for the main wash cycle and to add a second detergent dissolving rapidly in cold water in any way to the prerinse cycle, this would require two detergents of different composition which would not only be inconvenient, it could also give rise to confusion is use.